[GRASSLIST:2260] trend surfaces - can't get image of residuals

[Carlos Henrique Grohmann]

Hello all,

Things are starting to work on trend surfaces analysis.
I've converted my raster to sites and used sites.get() in R, so it comes as a
data.frame, and surf.ls() works well. using trmat.G() and rast.put(), I can get
the trend surface back into GRASS. 

The problem now is with residuals. I don't know how to put these values into a
matrix, to get an image or get it into GRASS.

if I use residuals(), I can see thet its output is the same as the $wz in
surf.ls() output...

here goes some of what I have:

> bases<-sites.get(G,slist="isobases",all.sites=F)
Warning message:
Old style sites file
> str(bases)
`data.frame':   3509 obs. of  4 variables:
 $ east : num  678148 672602 672608 680412 663768 ...
 $ north: num  7785498 7785472 7785468 7785468 7785462 ...
 $ id   : int  321 322 323 324 325 326 327 328 329 330 ...
 $ num1 : num  680 680 680 640 720 640 720 720 720 720 ...
 - attr(*, "nncols")= Named int  2 -1 1 0
  ..- attr(*, "names")= chr  "dims" "cattype" "dbl.att" "str.att"
> b2<-surf.ls(2,bases$east,bases$north,bases$num1)

> str(b2)
List of 11
 $ x   : num [1:3509] 678148 672602 672608 680412 663768 ...
 $ y   : num [1:3509] 7785498 7785472 7785468 7785468 7785462 ...
 $ z   : num [1:3509] 680 680 680 640 720 640 720 720 720 720 ...
 $ np  : num 2
 $ f   : num [1:21054] 1 1 1 1 1 1 1 1 1 1 ...
 $ r   : num [1:21] -59.237   4.521 -36.100 -22.345   0.472 ...
 $ beta: num [1:6]  945.2 -251.6  142.0   23.1  -48.5 ...
 $ wz  : num [1:3509] 241.8 166.0 165.8 211.4 -46.8 ...
 $ rx  : num [1:2] 657858 681048
 $ ry  : num [1:2] 7762302 7785498
 $ call: language surf.ls(np = 2, x = bases$east, y = bases$north, z =
bases$num1)
 - attr(*, "class")= chr "trls"

> b2r<-residuals(b2)
> str(b2r)
 num [1:3509] 241.8 166.0 165.8 211.4 -46.8 ...

thanks in advance
-- 
+-------------------------------------------------+
        Carlos Henrique Grohmann - Guano  
    Geologist - MSc Student at IGc-USP - Brazil
       Linux User #89721  ICQ: 214752832
+-------------------------------------------------+


> Hello all
>
> I'm trying to do some trend surface analysis with GRASS data in R, but I
> with some problems:
>
> 1 - when I get the raster from GRASS, surf.ls() doesn't accept it, since
> its not in x,y,z format:
>
>> str(isobase)
> List of 1
>  $ isobases.auto: num [1:241266] 771 770 769 768 767 ...
>>
>
> So, how can I change this to a format that surf.ls() understands?
>

isobase$isobases.auto is the z argument. You can generate the x by east()
of the object returned by gmeta(), and y by north() of this object. I'm
not sure how well surf.ls() scales to this number of points, though.

> 2 - I'll try several degrees of surfaces, so I'll use surf.ls(), but
> what about residuals? can I get them with residuals()?
>
Yes, residuals() should work. Again, scaling to this number of points is
an issue. On the other hand, the residuals and fitted values will drop
straight into the GRASS location.

Roger